Automatic control plug for electrical appliances



D. B. SCOVILLE March 19, 1935.

AUTOMATIC CONTROL PLUG FOR ELECTRICAL APPLIANCES Filed Aug. 18, 1953Patented Max'.l 19, 1935 PATENT OFFICE AUTOMATIC CNTRL PLUG FORELECTRICAL APPLIANCES David B. Scoville, Crystal Lake, lil.

Application august i8,

i933, Serial Nm 685,674.-

e: emma tcl. coo-es) This invention relates to improvements in auto1matic control plugs for electrical appliances, and more particularly forelectric toasters, grills and like utensils for the cooking orpreparation of food products wherein the application of heat requires`more or less accurate control.

The object of the invention is to provide a plug of substantially thesame size and design as the standard plug used for connecting the cordor conductor cable directly with the appliance and incorporating thereina compact time switch mechanism which can be set to operateautomatically to shut oil the current after the lapse of a given periodof time.

A further object of the invention is to provide for the varying of theperiod of time during which the current is supplied to the heatingelement of the appliance in order to regulate the application of heat tothe degree of toasting or cooking required.

A further object of the invention is to provide a device which may besubstituted for the stand ard plug oi a non-automatic electricalappliance and thus convert it into an automatic device at very littlecost. Perhaps the best example of its utility is in the ileld ofelectric toasters which are 'now being made to operate automatically,but at a cost considerably more than the ordinary or nonautomatic stylesand so much so that they are, at present atleast, beyond the means ofthe average pmchaser. Moreover, the vast majority of the toasters in useare of the non-automatic type, so that the ability to equip relativelyinexpensive toasters either old or new, to operate automatically bymerely substituting one plug for another at buts. triiiing additionalcost is a real boon to the users as well as to the manufacturers of Ithe older style devices.

Thus, while the idea of an automatic toaster is already a reality, themerit of the present invention resides in the simplicity and compactnessof the control mechanism which permits it to be incorporated in a plugwhich can be interchanged with the ordinary type of plug, withoutotherwise altering the toaster or its electrical connections.

A preferred embodiment of the invention is disclosed in the accompanyingdrawing, in which Figure l is a view of the plug in elevation;

Figure 2 is a view in longitudinal section taken on line 2-2 of Figurel;

Figure 3 is a view in elevation of the inside of the top section of theplug when the same is parted along the line 3-3 of Figure 2;

Figure 4 is aview in elevation of the inside of the bottom section ofthe plug when parted along the same line as in Figure 3 but in the direction oi the arrows llm-5i;

Ngure 5 is an enlarged detail view in cross section through the plug astaken on line 55 of Figure 2; and i3 Figure 6 is a detail view oi' theescapemerrt mechanism of the clock movement as taken on line 6 6 ofFigure 2.

lt will be observed at the outset that, so far as the electricalconnections are concerned, the l@ automatic plug follows closely theconstruction and design of the ordinary plug, in fact, theonly departureis a slight increase in the length to accommodate the added switchcontrol mechanism. is well known in the art, a more or less 35 standardtype of plug and plug connection has been developed for electricalhousehold appliences, namely, a casing of 'insulating material having apair of connectors exposed at one end to 'lt a pair of post-liketerminals on the appli- 20 ance, the plug itself being attachedto oneend of a cord having the usual connector at the other end for insertinginto a light socket or outlet.

Following the standard design,`the plug con sists of a flat elongatedcasing l of a suitable 25 insulating material such as bakelite which ismoulded in two sections 1a and 1b parted on a plane bisecting the casingin the direction of its Width. Bosses 2, 2 are moulded on the in-vterior of each half or section near opposite ends, 30

and screws 3, 3 are inserted through registering holes drilled andtapped in these bosses. When assembled the two halves of the casing 1provide a chamber in which are mounted the electrical conductors and thetime switch mechcmsm.

The electrical conductorsnin the plug have the form o! flat metal strips4 and 5 vand are anchored in the upper sect-ion 1a (Figure 3) by ,meansof rivets 6, 6 passing through enlarged 40 portions at their ends. AOneof the'strips 4 is continuous and lies along the side of the casing,whereas the other strip 5 is divided into two parts to forma simpleformof switch for making and breaking the circuit, as will presently bedescribed in greater detail. v

At the inlet end o f the plug the ends of the conductor strips4 and 5are provided with the usualbinding posts`7, '7 to which the ends of thewires forming the cord s are attached, said 5 cord-entering through anopening 9 in the end of the plug. At the outlet end of the plug are theendwise opening sockets 10, 10 before mentioned, and separated by thelongitudinally. elongated boss 3. within these sockets are the connectorclips 11, 11 electrically connected at their inner ends to the conductorstrips by the same rivets 6, 6 which anchor both to the casing section1.

Located centrally of the interior of the plug and between the twoconductor strips 4 and 5 is the time controlled switch mechanism, theparts thereof being rotative about two parallel axes spaced apart alongthe longitudinal center line of. the plug and extending transversely ofthe depth of the casing. This mechanism is essentially a variation ofthe so-called clock movement including a winding spring operativelyconnected with a train of gears controlled by a simple form ofescapement, and a driven cam member which acts directly upon the switchto make and break the circuit through the plug.

For convenience in assembly a part of the control mechanism, consistingof the gear train and escapement `of the clock movement, is mounted inone section (the lower section 1b) of the plug casing, while theremainder, including a winding spring and knob together with the cam aremounted on the other (upper) half of the casing carrying also theconductor strips 4 and 5. The parts of the control mechanism are thusseparated into groups which are assembled independently of eachother ontheir respective casing sections, the connections between them beingmade. by means of .spring fingers on the cam which register withprojections on the face of the adjacent Wheel of the clock movement whenthe two halves of the plug are assembled. y

Referring first to the4 parts carried by the upperhalf of the plugcasing, the winding spring 131s a simple form of clock spring coiledabout a cylindric boss 14 on the inner face of the casing section andhaving an axial bore in which is a shaft 15 (Figure 5). On the inner endof the shaft is fixed the cam 16 consisting of a disc having a deepmarginal fiange surrounding and enclosing the winding spring, the outerend of v the latter being fixed to a cam by means of a rivet 1'7 whichprojects from the outer face of the flange to provide a stop member fora pur- DOse to be later setforth. The inner end of the' spring isanchored to the boss 14 as by bending the end of the spring atrightangles, as at 13a, and inserting it into a slot 14 in the surfaceof the boss (Figure 5). Fixed to the outer end of the shaft 15 andexterior of the plug casing is the spring winding knob 18, preferably offrustro-conical shape having its tapered face knurled and direction andposition arrow marked on its circular end face as shown in Figure 1.

Formed in the face of the cam flange is a notch 16 having a radial stopshoulder on one side and a gradually inclined surface leading from theperiphery of the cam to the base of the notch. Now lying adjacentthe'cam and in a general tangential relation thereto is the longerportion 5Il of the conductor strip 5, bent to curve inwardly toward theLcam and thence beyond where it terminates in overlapping and normallyspaced relation to the shorter portion 5h of the same conductor strip.These overlapping portions thus form the make and break contact of thecircuit, and if desired may be provided with suitable contact points. Onthe longer flexible contact strip 5n is a finger .19 projecting towardthe cam and adapted in normal position to engage the cani notch .18% inwhich position cam are fixed a pair of spring ratchet fingers 20, 20curvedv to conform to the arcof a circle and riveted at theircorresponding ends at points diametrically opposite each other andmidway between the center and periphery .of the cam face. These ratchetfingers extend in the same direction, that is, clockwise from theirfixed ends and through an arc of and are bent outwardly from the face ofthe cam so that their free ends are spaced a short distance therefrom.Asheretofore explained, these ratchet fingers provide the connectionbetween the parts of the control mechanism carried by the upper halfsection of the casing just described, and those parts of the mechanismcarried by the lower section now to be described and identified.Briefly, the parts on the lower section constitute a simple clockmovement made up of two series of alternatingly intermeshing gears andpinions, one series being journalled on a stub shaft 21 anchored at oneend in the wall of the casing section and in axial alignment with thewinding spring 13, and the other series on a similar stub shaft 22spaced a short distance from it.

Since clock movements are well known, it will not be necessary toidentify each individual gear and pinion, except to point out that it ismade up of several units, 4each consisting of an inte,-l gral gear wheeland pinion, which progressively mesh with each other throughout thecomplete train, the gear of first unit of one series meshing with thepinion of the next unit, and so on. In this manner the desired gearreduction is obtained between the first and last units in the train. Andfinally, the rotation of the units is stamped therein and registeringwith the spring,

fingers 20, 20 on the cam. This gear wheel 23 meshes with the pinion ofa unit 24 on the shaft.

22, which in turn drives a similar unit-25 on the shaft 21, this lastunit driving still another 4unit 26 on the shaft 22. Now, the gear wheelof this last unit acts as the escapement wheel, having pointed teeth asshown in Figure 6. On the shaft 2l opposite the escapement wheel is adisc 27, somewhat thicker andheavier than the gear wheels and having aboss 27a to which is fixed the escapement lever 28 consisting of a metalstrip vbent in U-shape with inwardly curved fingers engaging the teethof the escapement wheel. The disc or balance wheel 27 rocks oroscillates on the shaft 2l with the escapement movement and by reason ofits weight and-inertia controls the timing of the movement. 2

As hereinbefore pointed out, the gear train or clock movement justdescribed is a self-contained unit wound by the lower section of theplug casing, and in assembling the two sections the projections orratchet teeth 23'l on the gear wheel 23 register with the spring fingers20 on the cam 16 and establish a pawl and ratchet connection between thetwo groups or parts of the switch control mechanism.

The manipulation of the switch control mechanism isquite simple,consisting merely in turning the knob in a clockwise direction throughsomething less than one complete turn for the maximum heating period;about one-half turn for the minimum period and to an intermediateposition for one corresponding intermediate period of heating. Thesestages of heat duration are gauged to the degree of toasting that may bedesired, as for example, well done or dark, slightly done or light andmedium done. Suitable position indicators are marked on the casingaround the edge of the knob together with spaced markers correspondingin numberto the projections or ratchet teeth 23a over which the springpawl fingers 20 click when turning the knob in the clockwise directionto wind the spring.

Thus assuming that the toaster is connectedl with the knob in the o ffposition and the bread to be toasted is in place, the operator merelyturns the knob in a clockwise direction to the position for the desireddegree of toasting and then releases it. Now in turning the knob, thecam 16 rotates with it but its rotation is not transmitted to the geartrain because the ratchet fingers 20 on the cam merely click over theteeth 23a on the rst wheel 23 of the clock movement. However, with theinitial turning of the cam, the circuit is closed by the cam action ofthe finger 19 on the switch member 5a sliding out of the cam notch 16aand into the flange of the cam. Moreover, the spring 13 is wound by therotation of the cam, so that on releasing the knob the cam is turned inthe oppov site direction under `the action of the spring unwinding, butits return movement is regulated by the clock movement .which nowfunctions through the pawl and ratchet connection.' 'I'his returnmovement of the knob and cam is relatively slow, taking, say, one ormore minutes, depending upon the length of time required for toasting,and when the return movement is complete the cam comes to a stop at itsstarting point simultaneously opening the circuit as the' finger 19 onthe switch member 5 again'enters the cam slot.

This procedure is repeated for each toasting operation, in each case theduration of the toast- I n ing being controlled by the position to whichthe winding knob is turned from the oil position before releasing it.And in this connection it will be noted that the mechanism is sodesigned that one revolution of the knob is the maximum of the windingmovement. Therefore, to prevent an inexperienced person from turning theknob in excess of this limit, the stop member 17 is provided on the cam.Thus when the knob has been turned through one revolution, the stop 17will strike the finger 19 and prevent its iurther turning. i

vSince different makes of toasters vary somewhat in the intensity ofheat andtherefore the period required for toasting, the time adjustmentsof the plug can also be utilized in adapting it to the particulartoaster to which it is applied, so that once the required period of timefor proper toasting is determined by experiment, uniform toasting can beobtained thereafter by turning the knob to the same point. In fact, itwould be an obvious expedient to provide means for limiting the turningof the knob to any desired amount, and when once set there would be noneed thereafter for visually. determining the point at which the knob isto be released. In other words, it is equally if not more important thatthe lplug be adjustable to different makes oi' appliances, as it is thatit can be regulated for diierent degrees of toasting, since uniformperformance is the essential requirement.

In conclusion, therefore, the merit of the inventionresides in itsconstruction as well as its application in the art. Thus, aside from thefact that makes possible the automatic operation of electric toastersand like appliances at but little additional cost and without alteringits construction or design, the mounting of a simple yet practical timecontrolled switch mechanism within a plug of substantially standarddimensions is a novel accomplishment, particularly in the grouping ofthe parts into separate units mounted in the sections of a two-partcasing, a construction that aifords ease of manufacture and assembly,not to mention the simplicity of repairs and replacement of parts.

Having set forth 'a preferred embodiment of my invention, I claim:

1. In a connector plug for electrical appliances comprising a casingdivided longitudinally into sections, the combination of a contactswitch, a switch operating cam and a winding spring mounted in onesection and a clock movement mounted in the other section and includinga' disc adapted in the assembly of said casing to be positioned face toface with said cam, and pawl and ratchetmembers carried by said cam anddisc and providing a detachable connection between said cam and clockmovement.

.2. In a connector plug for electrical appliances comprising a casingdivided into sections and nav- 'ing a switch mounted therein, thecombination of a rotative cam mounted on one of said sections i andhaving operative connection with said switch whereby the latter isshifted into circuit closing position in the rotation of said cam from anormally oif" position, a coil spring mounted in said section adjacentsaid cam and connected therewith for winding in the rotation of saidcam, and a clock movement mounted in the other section and including adisc rotative on an axis coincident with the axis of said cam, thelatter having resilient fingers adapted to. engage teeth on the face ofsaid disc to interconnect the same when the sections of said casing areassembled.

3. In a connector plug for electrical appliances comprising a casingdivided longitudinally into two half sections, the combination of aswitch, a manually rotative switch operating cam, and a winding springmounted in one of said sections, and a clock movement mounted in theother section and including a gear wheel rotative on an axis coincidentwith the axis of said cam, the latter having resilient fingers adaptedto engage teeth on the face of said gear wheel to interconnect the samewhen the sections of said casing are assembled. f

4. In a plug connector for electrical appliances comprising aninsulatedcasing parted longitudinally into two sections and enclosing aswitch including a flexible metal strip adapted to be flexed into andout of circuit closing position, the combination of a rotative camhaving a notch in its periphery to receive a projection on said contactstrip in the oiI position of said switch, a

manually rotative finger piece exterior said castion between 'theunitsmounted in their respective sections in the assembly of the casing.

5. In a plug connector for electrical appliances comprising an insulatedcasing parted 1ongitudinally into two sections, the `combination of a.switch including a metal contact strip adapted to be flexed into and outof circuit closing position, a cam adapted for bearing contact at itsperiphery with said strip and having a notch therein normally positionedto receive a projection on said strip in the olf position of saidswitch, a manually operative finger piece exterior said casing forrotating said cam disc, and a coil spring adapted to be wound in therotation of said ilnger piece, all oi' said parts forming a unit mountedin one of said casing sections, and a clock movement journalled on stubshafts supported by the other section of the casing and including a gearwheel spaced from and in axial alignment with said cam and havingannularly arranged projections in the face thereof, and spring fingersmounted on the face oi' said cam and adapted to engage the projectionson said gear wheel to connect the clock movement in one section with 1the parts in the other section when the same are assembled.

DAVID B. SCOVILLE.

